From Longman Dictionary of Contemporary Englishstereoster‧e‧o1 /ˈsteriəʊ, ˈstɪər- $ ˈsterioʊ, ˈstɪr-/ noun (plural stereos) 1 
(also stereo system) [countable]TCR a machine for playing records, CDs etc that produces sound from two speakers a stereo with good speakerson a stereo He was listening to the Beatles on the car stereo.2 → in stereo → personal stereo
(also stereo system) [countable]TCR a machine for playing records, CDs etc that produces sound from two speakers a stereo with good speakerson a stereo He was listening to the Beatles on the car stereo.2 → in stereo → personal stereoExamples from the Corpus
stereo• They told us that you could get a stereo in Saigon for about a third of what it cost in the States.• Had these people got bored with making cars and stereos and aerosols? were they going to start making history?• Eventually, environmental health officers seized Mary Carruthers' stereo system and speakers after a petition from neighbours.• When the stereo sends audio signals to the electrodes in the speaker, sound comes out of the perforations.on a stereo• Two excerpts from Scriabin's Poem of Fire were recorded on stereo discs on 12 March 1932.stereostereo2 (also stereophonic) /ˌsteriəˈfɒnɪk◂, ˌstɪər- $ ˌsteriəˈfɑːnɪk◂, ˌstɪr-/ adjective TCRusing a recording or broadcasting system in which the sound is directed through two speakers → mono, quadraphonic stereo equipmentExamples from the Corpus
stereo• A wide-screen projection system was used in combination with stereo lenses to produce a three-dimensional effect.• This gives them overlapping fields of view and the true stereo vision that they need to capture their prey.Origin stereo2 (1900-2000) stereophonic ((1900-2000)), from Greek stereos “solid” + English phonic 